Integral laminate photographic units comprising developing composition-spreader sheets containing a polymeric acidifying layer

ABSTRACT

Novel system for forming visible images wherein an aqueous alkaline processing composition is applied between a first sheet comprising a photosensitive element and a second sheet including an acid-neutralizing layer, said sheets being adapted for being maintained together after application of the processing composition. In a preferred embodiment, a system is disclosed for forming negative images wherein a developed and fixed negative image in silver is provided with a transparent overlay through which the image may be viewed. In another disclosed embodiment, an image in color, which may be a positive transfer image, is provided with such a transparent overlay.

United States Patent [1 1 Land [ 1March 20, 1973 INTEGRAL LAMINATEPHOTOGRAPHIC UNITS COMPRISING DEVELOPING COMPOSITION- SPREADER SHEETSCONTAINING A POLYMERIC ACIDIFYING LAYER [75] Inventor: Edwin H. Land,Cambridge, Mass.-v

[73] Assignee: Polaroid Corporation, Cambridge,

Mass.

[22] Filed: July 29, 1971 [211 App]. No.: 167,455

Related U.S. Application Data [63] Continuation-in-part b? Ser. 'NoI888,919,

Dec. 29 1969.

[52] [1.8. C]. ..96/61 M, 96/3, 96/29 D, 96/29 R, 96161 M, 96/66 R [51]Int. Cl ..G03c 5/38, G030 5/54, G03c 7/00 [58] Field of Search ..96/3,29 R, 29 D 56] References Cited UNITED STATES PATENTS 3,362,819 Land..96/3

3,549,364 12/ i970 Morse ..96/29 R Primary Examiner-J. Travis BrownAssistant Examiner-Alfonso T. SuroPico Attorney-Charles Mikulka et al.

[57] ABSTRACT 7 Novel system for forming visible images wherein an Itransfer image, is provided with such a transparent overlay.

22 Claims, No Drawings INTEGRAL LAMINATE PI'IOTOGRAPHIC UNITS COMPRISINGDEVELOPING COMPOSITION- SPREADER SHEETS CONTAINING A POLYMERICACIDIFYING LAYER This is a continuation in part of application Ser. No.888,919 filed Dec.29, 1969.

BACKGROUND OF THE INVENTION U.S. Pat. No. 3,343,958 discloses a one-stepsystem for forming a developed and fixed negative image which requiresno stabilizing aftertreatment, e.g., washing to remove spend processingcomposition and/or printcoating. According to this patent, aphotosensitive element comprising a light-sensitive silver halide layeris exposed to form a developable image and the thus exposed element isthen developed with an aqueous alkaline processing compositioncontaining at least one silver halide developing agent and a silverhalide solvent system which will fix the developed image by forming fromundeveloped silver halide a transparent silver complex which will notsubsequently precipitate as image silver. The silver halide solventsystem employed to form this stable, transparent silver complex consistsessentially of the combination of cysteine (aamino-B-mercaptopropionicacid) and a nitrogenous base, preferably a volatile nitrogenous base.Examples of useful nitrogenous bases include: ammonia, sec. amylamine,ethylamine, n-butyl-amine, allylamine, diethylamine, dipropylamine,trimethylamine, triethanol amine, diethylene triamine, triethylenetetramine, N-hydroxyethyl propylene diamine, trimethylene diamine,ethylene diamine, aminoethyl ethanol amine, hydroxyethyl diethylenetriamine, tetraethylene pentamine, quanidine hydrochloride, piperidine,pyrrolidine, 2,5-dimethyl piperazine, polyethylene imine, symmetricaldimethyl hydrazine and unsymmetrical dimethyl hydrazine.

This silver halide solvent system is preferably employed in processingcompositions including the silver halide developing system described andclaimed in the application of Meroe M. Morse, Ser. No. 438,044, filedMar. 8, 1965 and which was abandoned in favor of application Ser. No.690,728, filed Dec. 15, 1967, now U.S. Pat. No. 3,549,364 as acontinuation-in-part thereof. As is disclosed in these applications, thenecessity for some aftertreatment, e.g., washing, to prevent the harmfuleffects resulting from the presence of exhausted and/or unexhausteddeveloping agent is greatly reduced, if not obviated, by employing asthe developing system the combination of a high concentration of alow-energy silver halide developing agent and an extremely lowconcentration of a high-energy silver halide developing agent.

Many so-called high-energy developing agents are known in the art.Preferred are the aminophenols, particularly 4-aminophenols containing alower alkyl, lower alkoxy and/or amino group in a position or positionsortho to the hydroxyl group. Particularly useful examples of suchhigh-energy silver halide developing agents include2,4-diaminoortho-cresol, 4-amino-2,6-

dimethyl-phenol and 2,6-dimethoxy-4-amino-phenol.

Other examples of suitable high-energy silver halide developing agentsmay be found in U.S. Pat. Nos. 3,091,530, 3,108,001 and others.

Particularly useful low-energy silver halide developthose which havesubstantially colorless oxidation products and/or are volatilized fromthe image, particularly the ascorbic acids, such as ascorbic acid,isoascorbic acid, etc., and hydroxylamines, e.g.,N,N-diethylhydroxylamine, and N.,N,-dimethoxyethyl-hydroxylamine. N,N-dimethoxyethyl-hydroxylamine. hydroxylamine silver halide developingagents include those disclosed in U. S. Pat. Nos. 2,857,276, 3,287,125and others.

As stated above, the high-energy silver halide developing agent is usedin extremely low concentrations, i.e., a concentration ineffective, ifused as the sole developing agent, to develop appreciable negativedensity, e.g., less than about 0.3, within the predetermined, usuallyvery short, processing period. Although the low-energy silver halidedeveloping agent is used in substantial concentrations, it too isineffective to develop appreciable negative density within thepredetermined processing period if used in that concentration as thesole developing agent. However, this ing an exposed silver halideemulsion to obtain a silver image of excellent density and detailwithout leaving any reagents capable of impairing the quality of theimage.

In addition to the foregoing ingredients, processing compositionsemployed in such systems for forming a developed and fixed negativeimage may contain an alkaline material necessary for initiatingdevelopment such as sodium or potassium hydroxide, sodium carbonate,etc., and they may contain other ingredients performing specific desiredfunctions, e.g., a viscous film-formingreagent such as hydroxyethylcellulose, sodium carboxymethyl cellulose, etc., antifoggants, toningagents and the like. In systems employing the aforementioned. silverhalide solvent system, the processing composition may also contain asmall amount of sodium or potassium thiosulfate, which, as is disclosedin the aforementioned U.S. Pat. No. 3,343,958 has been found to lowerappreciably the imbibition time necessary to obtain a fixed negativeimage of the desired density and contrast.

To prepare a negative image with the above-mentioned processingcompositions, the exposed photosensitive element is contacted with theprocessing composition for a suitable period of time to develop and fixthe image. A particularly useful procedure for applying the processingcomposition is by spreading the composition containing the viscousreagent in a substantially uniform layer between the thus exposedelement and a superposed spreader sheet. After the development period,the spreader sheet is removed to reveal the developed and fixed negativeimage. Such procedures employing a spreader sheet are disclosed, forinstance, in the illustrative examples of the aforementioned patent andapplications.

In the procedures described above, following development it is necessaryto separate the spreader sheet to reveal the image. This spreader sheetis then discarded, thereby requiring the photographer to find a place todeposit it until it may be disposed of. The objections to storing it inones pocket or carrying a spe- N,N-diethoxyethyl-hydroxylamine,

cial litter container will be apparent. It would therefore be desirable.to device a system which obviates these objectional features.

It was first thought that this could be accomplished by employing as thespreader sheet one of the known transparent sheet materials which wouldbe retained on V the negative image to provide as the final product asheet and the superposed photosensitive element to ef-' fectdevelopment, after a short period of time the reagent dries sufficientlyto act as an adhesive effectively bonding and retaining these materialsin superposition. It was found, however, that in such a lamination orsandwich, after a relatively short period of time, e.g., 24 hours, tinypin holes appeared in the silver areas of the negative image, producingminute transparent areas which reproduced in positive prints obtainedtherefrom as corresponding tiny black dots in the highlight areas of theprint. In other words, while a negative image produced in accordancewith the teachings of the aforementioned patent and application wasextremely stable, as evidenced by the fact that such negatives with noaftertreatment were found to exhibit no density fading or densityincrease in highlights when stored for over two years, when the finalproduct was in the form of a sandwich containing the transparentoverlay, something happened which caused removal of image silver toproduce the tiny transparent dots mentioned previously. The exact reasonfor this phenomenon is not clearly understood. However, it is believedto be initiated by the fact that the processing composition is confinedand hence removal of moisture and resulting drying time is materiallyextended over systems wherein the surface of the developed negative isfully exposed to air.

One embodiment of this invention is directed towards obviating thisproblem so as to provide a stable developed and fixed negative imageprovided with a transparent overlay through which the image may beviewed.

Procedures have also heretofore been known wherein a visible image incolor is obtained by developing an exposedphotosensitive elementcomprising at least one light-sensitive silver halide layer having a dyeimage-providing material associated therewith with an aqueous alkalineprocessing composition. Multicolor images are so obtained by employingphotosensitive elements containing more than one such silver halidelayer and associated dye image-providing material, the preferred suchfilm unit for forming multicolor images being of the so-called tripackconfiguration including a blue-, a greenand a red-sensitive silverhalide layer having associated therewith, respectively, a yellow, amagenta, and a cyan dye im age-forming material which may be a completedye or a dye intermediate, e.g., a color coupler. Such color processesgenerally speaking may be referred to as being additive or subtractivecolor systems. A particularly useful system for forming color images isone of the known color diffusion transfer systems wherein an exposedfilm unit of the foregoing description is developed to provide, as afunction of such exposure and development, an imagewise distribution ofmobile and diffusible dye image-providing material which is thentransferred, at least in part, by diffusion, to a superposed dyeablestratum to impart thereto a color transfer image which may be a positiveor a negative color image, depending upon the particular photographicsystem employed. In general, the dye image-providing materials employedin such color processes may be defined as being either initially mobileand diffusible materials which are selectively rendered immobile ornon-diffusible; or initially immobile and non-diffusible materials whichare selectively rendered mobile and diffusible as a function ofdevelopment. As examples ofthe former type of imageproviding materialsand systems employing them to prepare color images, mention may be madeof those disclosed, for example, in U.S. Pat. Nos. 2,647,049; 2,661,293;2,698,244; 2,698,798; 2,802,735; 2,774,668; and 2,983,606; as examplesof thelatter type of image-providing materials and systems employingthem to prepare color images, mention may be made of those disclosed,for example, in U.S. Pat. Nos. 3,443,939; 3,443,940; 3,227,550;3,227,551; 3,227,552; 3,227,554; 3,243,294; and 3,445,228.

One particularly useful class of dye image-providing materials are dyedevelopers, i.e., dyes which are also silver halide developing agents.Photographic systems employing dye developers are disclosed in theaforementioned U.S. Pat. No. 2,983,606 as well as in many subsequentlyissued patents and since such photographic systems are well known in theart, further detailed description is not necessary.

It is also advisable to adapt these color systems of the processingcomposition, it has been found that the stability and/or quality of theresulting image suffersunless means are provided for lowering the pHafter sub-- stantial development and color image formation has beencompleted. To accomplish this objective it has heretoforebeen suggestedthat the film unit contain an acid neutralizing layer, e.g., apolymericacid layer. Color systems employing such pH-reducing means aredisclosed,for example, in U. S. Pat. No. 3,362,819. In diffusiontransfer systems, this layer is usually associated with the dyeablestratum or image-receiving layer, although systems are also knownwherein the acid-neutralizing layer is associated with thephotosensitive strata, e.g., with the silver halide layer or layers.

It is to such systems wherein an alkaline processing composition isapplied between a first sheet material comprising an exposedphotosensitiveelement and a second sheet material or spreader sheet toprovide a visible image, that this invention is directed.

SUMMARY OF THE INVENTION In accordance with this invention, theaforementioned problems in the various film systems such as thosedescribed above are obviated by employing as the second (spreader) sheetor overlay, a sheet material, preferably transparent for viewingpurposes, having a layer of a material which will remove, neutralize orotherwise render innocuous a sufficient quantity of unexhausted alkalinematerial following development and substantial image formation. Thislayer may be a polymeric acid layer of the type described in theaforementioned U. S. Pat. No. 3,362,819.

DESCRIPTION OF PREFERRED EMBODIMENT In the preferred embodiment thislayer contains a polymeric acid and means are also provided forpreventing premature interaction between the alkaline ions and thepolymeric acid, i.e., pH reduction prior to development of the exposedphotosensitive element. In a particularly preferred form, the polymericacid is disposed in a layer between the transparent sheet material andan inert alkali-permeable spacer layer which serves to time controldiffusion through this layer to the underlying polymeric acid layer andsubsequent pH reduction.

As was mentioned previously, this invention relates to photography and,more particularly, to photographic procedures which are litter-free,namely do not involve the use in the development process of materialswhich must latter be discarded, thereby avoiding all of theinconveniences inherent in prior systems of this nature.

A primary object of this invention is to provide novel photographicprocedures of the foregoingdescription.

Another object is to provide novel systems wherein a photosensitiveelement or film unit is developed by applying a viscous aqueous alkalineprocessing solution between the exposed element and a superposed secondor spreader sheet including an acid-neutralizing layer to provide, asthe desired photographic print, a sandwich" comprising the visible imageformed as a function of development and the superposed spreader sheet,which image is viewable without separation of the respective sheets.

Another object is to provide novel procedures wherein an exposedphotosensitive element is developed and fixed in a single step byspreading an aqueous alkaline processing composition between the thusexposed element and a superposed transparent element to provide, as thefinal product, a highly stable negative image in the form of a sandwichconsisting essentially of the developed and fixed negative image, thesurface of which is adhered to the transparent element through theadhesive action of the spent or exhausted processing compositioninterposed therebetween.

Still another object is to provide a novel process wherein aphotosensitive element comprising a lightsensitive silver halide layeris exposed to form a developable image; the thus exposed element is thendeveloped and fixed in a single step by spreading between the exposedelement and a superposed transparent element comprising a transparentsheet material bearing on the side to be placed closest to thephotosensitive element a polymeric acid layer, a viscous aqueousalkaline processing composition containing a silver halide solventsystem comprising the mixture of cysteine and a nitrogenous base and asilver halide developing system comprising the combination of a smallamount of a high-energy silver halide developer and a large amount of alow-energy silver halide developing agent; and the respective elementsare retained in superposition as the final product.

Yet another object is to provide a sandwich of the foregoing descriptionincluding a photographic image in color. I

A still further object is to provide a positive color transfer imagehaving a transparent overlay of the foregoing description through whichthe color image may be viewed.

Other objects of the present invention will in part be obvious and willin part appear hereinafter.

The invention accordingly comprises the several steps and the relationand order of one or more of such steps with respect to each of theothers, and the product possessing the features, properties and therelation of elements.

As was mentioned previously, the present invention is directedto'photographic procedures wherein an exposed photosensitive element isdeveloped by applying an alkaline processing composition between theexposed element and a superposed spreader sheet to provide a visibleimage which may be viewed without separation of this spreader sheet. Thepresent invention therefor contemplates systems wherein a spreader sheetis employed to facilitate application of a viscous alkaline processingcomposition in a substantially uniform layer over the surface of thefilm unit to initiate development and thereafter need not be discarded.I

One photographic system particularly contemplated by this invention isthe one-step system for forming a developed and fixed negative imagedescribed in U. S. Pat. No. 3,343,958 and described with moreparticularity in the Background of the Invention. As was also mentionedin the Background of the Invention, when a conventional transparentsheet material is employed as this spreader sheet, instability of thenegative image occurs. This instability manifests itself in a relativelyshort period of time, say, for example, after 24 hours as tinytransparent dots or pin holes in the areas of developed silver, whichreproduce in positive prints obtained therefrom as tiny black dots inthe highlight (non-image) areas. In accordance with the presentinvention it has been discovered that this.

problem may be effectively obviated by employing as the spreader sheet atransparent sheet material having a layer to which the alkaline ions maydiffuse following development and be captured and retained in place,e.g., by' neutralization. This layer may, for example, comprise apolymeric acid. Stated another way, the essence of the present inventionis the discovery that the problem of pin holes in silver areas of thenegative image formed by applying the viscous processing fluid betweenthe exposed photosensitive element and the superposed spreader sheet andretaining these elements in superposition as the final product, may beobviated by employing as this spreader sheet an elementincluding meansfor lowering the pH of the spent processing fluid to at least about pH 8and preferably below pH after image formation.

The spreader sheet (transparent overlay) contemplated for use in thisinvention comprises a transparent sheet material, for example, atransparent plastic such as polyethylene terephthalate, a vinyl resin,e.g., a copolymer of vinyl acetate and vinyl chloride, a cellulose estersuch as cellulose acetate, cellulose triacetate, cellulose butyrate,etc., carrying a polymeric acid layer which removes alkaline ions andlowers the pH by diffusion of these ions from the surface of thenegative image and/or the processing fluid to this layer where they areprecipitated.

Useful polymeric acids include various polymers containing carboxylic orsulfonic acid groups which are capable of forming salts with thealkaline ions, as well as polymers containing potential acid-yieldinggroups, such as anhydrides, lactones, etc. The acid polymers found to bemost useful are characterized by containing free carboxyl groups, beinginsoluble in water in the free acid form, and by forming water-solublesodium salts. One may employ polymers containing carboxylic acidanhydride groups, at least some of which preferably have been convertedto free carboxyl groups prior to imbibition. While the most readilyavailable polymeric acids are derivatives of cellulose or of vinylpolymers, polymeric acids from other classes of polymers may be used. Asexamples of specific polymeric acids contemplated as being used in thisinvention, mention may be made of dibasic acid halfester derivatives ofcellulose, which derivatives contain free carboxyl groups, e.g.,cellulose acetate hydrogen phthalate, cellulose acetate hydrogenglutarate, cellulose acetate hydrogen succinate, ethyl cellulosehydrogen succinate, ethyl cellulose acetate hydrogen succinate,cellulose acetate hydrogen succinate hydrogen phthalate; ether and esterderivatives of cellulose modified with sulfoanhydrides, e.g., withorthosulfobenzoic anhydride; polystyrene sulfonic acid; carboxymethylcellulose; polyvinyl hydrogen phthalate; polyvinyl acetate hydrogenphthalate; polyacrylic acid; acetals of polyvinyl alcohol with carboxyor sulfo substituted aldehydes, e.g., 0-, m-, or p-benzaldehyde sulfonicacid or carboxylic acid; partial esters of ethylene/maleic anhydridecopolymers; partial esters of methylvinyl ether/maleic anhydridecopolymers; etc.

It will be appreciated that the pH-reducing action by the polymeric acidshould be controlled so as not to interfere with the development step.In order to prevent premature pH reduction, the acid groups arepreferably distributed in the acid polymer layer'such that the rate oftheir availability to the alkali is controllable, e.g., as a function ofthe rate of swelling of the polymer layer, which rate in turn has adirect relationship to the diffusion rate of the alkali ions. Thedesired distribution of the acid groups in the acid polymer layer may beeffected by mixing the-acid polymer with a polymer free of acid groupsor lower in concentration of acid groups and compatible therewith, or byusing only the acid polymer, but selecting one having a relatively lowerproportion of acid groups.

In the preferred embodiment of this invention, an inert spacer layer ortiming layer is provided over the polymeric acid layer to obtain stillfurther improvements in control of the pH reduction by the polymericacid layer. This spacer layer comprises a polymer, or mixture ofpolymers, inert to alkali but through which the alkaline ions maydiffuse to the polymeric acid layer. As examples of useful polymericmaterials for this timing layer, mention may be made of polyvinylalcohol, a partial acetal of polyvinyl alcohol, e.g., partial polyvinylbutyral, gelatin, a cyanoethylated polyvinyl alcohol, a polyvinyl amide,a graft polymer, e.g., a polyvinyl amide graft polymer such as the graftcopolymer of diacetone acrylamide and acrylamide on polyvinyl alcohol,etc.

Polymeric acid layers and timing layers of the foregoing descriptionhave heretofore been contained on image-receiving elements furthercontaining a dyeable stratum and hence are heretofore known in the artof color diffusion transfer photography. Accordingly, such layers per secomprise no part of this invention. As examples of patents pertaining tocolor im age-receiving elements containing such layers, mention may bemade of U. S. Pat., No. 3,362,819 issued to Edwin H. Land;

No. 3,419,389 issued to Howard C. Haas and Henry S.

Kolesinski; No. 3,421,893 issued to Lloyd D. Taylor; and No. 3,433,633issued to Howard C. Haas. Timing layers comprising a polyvinyl amidegraft copolymer, mentioned previously, are described and claimed in thecopending application of Lloyd D. Taylor, Ser. No. 790,747 filed Jan.13, 1969, now U.S. Pat. No. 3,575,701.

In a preferred form of this invention, the processing composition iscontained in a frangible or rupturable container of the type heretoforeknown in the art and disclosed for example, in U. S. Pat. Nos. 2,543,181and 2,634,886, issued to Edwin H. Land.

To prepare a negative image according to this invention, an exposedphotosensitive element comprising a light-sensitive silver halide layeris developed by applying a viscous aqueous alkaline processingcomposition of the type previously described between the thus exposedelement and a superposed transparent element of the foregoingdescription. After a suitable development time, e.g., 30 seconds, afully developed and fixed negative image is obtained. The spreader sheetwhich was adhered to the surface of this negative image is retained asan integral part of the finished product, rather than being a wastematerial requiring disposal. Negatives prepared in accordance with thisinvention have been found to be highly stable, requiring noaftertreatment. They may be employed subsequently in standardphotographic techniques for obtaining one or more positive prints of theoriginal subject matter.

The following examples show by way of illustration and not by way oflimitation the practice of this invention.

EXAMPLE 1 A photosensitive element having a gelatino silver halideemulsion on a transparent film base was exposed and then developed byspreading between the thus exposed emulsion and a superposed subcoatedcellulose triacetate spreader sheet, at a gap of 0.0022, a viscousprocessing composition containing the following proportions ofingredients:

Water 902.0 cc Hydroxyethyl cellulose 4L5 g. Sodium sulfite 33.0 3.Potassium thiosulfate 14.0 g.

Ascorbic acid 60.0 g. 2,4-diamino-orthocresol 2.0 g. cysteine 2.2 g.diethylamine 50.0 cc. Sodium hydroxide 25.0 g.

After an imbibition time of about 30 seconds, an excellent negativeimage was obtained. The spreader sheet was retained on the negative andthe resulting sandwich was stored at room temperature. After about 24hours tiny pin holes were observed in the areas of developed silver.These tiny transparent areas reproduced as corresponding tiny black dotsin the highlight areas of positive prints obtained from this negativeimage. 1

EXAMPLE 2 A spreader sheet was prepared by applying to the subcoatedsurface of a cellulose triacetate sheet an aqueous solution comprising70 parts by weight of poly-(. ethylene/maleic anhydride) [commerciallyavailable from Monsanto Chemical Co. as DX Resin Grade 840-1 l-03] and30 parts by weight ofElvanol 70-05 (trademark of E. I. duPont de Nemoursand Co. for a low viscosity, completely hydrolyzed polyvinyl alcohol).The solution was dried to provide a polymeric acid layer about 0.4 mil.thick. Over this was applied a timing layer about 0.15 mil. thickcomprising a graft copolymer of diacetone acrylamide and acrylamide onpolyvinyl alcohol prepared in the manner described in the aforementionedcopending application, Ser. No. 790,747. The procedure of Example 1repeated, substituting this spreader sheet for the spreader sheetemployed in Example 1, the processing fluid being spread between theexposed photosensitive element and the coated side of the spreadersheet. An excellent image similar to that obtained in Example 1 wasformed. Again, the spreader sheet was retained as an integral part ofthe final product. Negative images prepared in the manner described inthis example failed to exhibit the pin hole effect after months ofstorage, thereby indicating that the stability problem illustrated inExample 1 had been obviated.

EXAMPLE 3 A negative image containing the transparent overlay preparedas in Example 2 was subjected to a standard heat-humidity storage testby storing it for 40 hours at separation of the spreader sheet from thefilm unit or' photosensitive element containing the image. Preferredsystems of this nature are those wherein a color image is imparted, bydiffusion transfer, to a dyeable stratum and a white reflecting agent isprovided between the thus formed image and the photosensitive strata,e.g.,

. on the side of the dyeable stratum opposed from the viewing surface ofthe film unit, so that the color image can be viewed, withoutseparation, as a reflection print. As an example of such color systems,mention may be made of those described in the copending applications ofHoward G. Rogers, Ser. No. 39,646, now US. Pat. No. 3,594,165, and Ser.No. 39,666, now US. Pat. No. 3,594,164, both filed May 22, 1970. Theseapplications disclose systems wherein a processing composition isapplied between a dimensionally stable support layer, e.g., spreadersheet, and the coated surface of a photosensitive element including atleast one light-sensitive silver halide layer and associated dyeimageproviding material, a layer of reflecting agent, e.g., a whitepigment, and, a dyeable stratum contained on a dimensionally stabletransparent support member, to v I provide a color transfer imageviewable, by reflected light, through the transparent support member ofthe photosensitive element. In such systems, it is often desirable, ifnot necessary, for image stability and/or optimum image quality, toprovide neutralizing means to lower the pH after substantial color imageformatiori. The present invention provides such neutralizing 1 the useof the present invention in color photography,

the color image so formed being a transfer image viewable, withoutseparation, as a reflection print.

EXAMPLE 4 Over the coated surface of a conventional type multicolornegative employing dye developers and comprising an opaque supportmaterial containing the following layers:

a layer of a cyan dye developer, 1,4-bis-(B-hydroquinonyl-a-methyl-ethylamino)-5 ,8-dihydroxyanthraquinone dispersedin gelatin;

2. a red-sensitive gelatino silver iodobromide emulsion;

3. a gelatine interlayer;

4. a layer of a magenta dye developer, 2-(p-[B- hydroquinonylethyll-phenylazo )-4-isopropoxyl naphthol dispersed in gelatin;

5. a green-sensitive gelatino silver iodobromide emulsion;

6. a gelatin interlayer;

7. a layer of a yellow dye developer 4-(p-[B-hydroquinonylethyl]-phenylazo)-3-(N-hexylcarboxamido)-1-phenyl-5-pyrazolonedispersed in gelatin;

8. a blue-sensitive gelatino iodobromide emulsion; and

9. a layer containing 4-methylphenyl hydroquinone dispersed in gelatinwas coated the following additional layers:

10. a white reflecting layer containing about 650 mgs./ft. of titaniumdioxide; 55 mgsJft. of gelatin; and 15 mgs./ft. of CAB-O-SIL (trademarkof Godfrey L. Cabot for a fire-dry 99 percent pure fumed silica with aparticle size of 0.015 micron); and

11. a dyeable stratum comprising a 2:1 mixture, by

weight, of polyvinyl alcohol and poly-4-vinylpyridine, and including adevelopment restrainer, l-phenyl-S- mercaptotetrazole to provide amulticolor film unit containing the photosensitive strata and associateddye image-providing material and the dyeable stratum or receiving layerseparated by a layer of white reflecting agent. This film unit was thenexposed through the coated surface and then developed by applyingbetween the thus exposed element and the coated surface of a spreadersheet comprising a transparent polyester base containing a 72.5 mixture,by weight, of polyethylen elmaleic anhydride copolymer and polyvinylalcohol at a coverage of about 1,000 mgs./ft., as the acid-neutralizinglayer, and a spacer layer comprising a 1:9 mixture of styrene/maleicanhydride copolymer and vinyl acetate at a coverage of about 1,000mgs./ft., at a gap of about 0.0050 inch, a processing fluid containingthe following proportions of ingredients:

to provide a multicolor image viewable the spreader sheet as a positivereflection print. When compared with a control prepared in the samemanner except the spreader sheet was a standard transparent sheetcontaining no neutralizing layer, the aforementioned print (preparedwith a spreader sheet including an acidneutralizing layer in accordancewith this invention) was significantly better, particularly in therendering of the blues, greens and cyans.

The present invention is also useful in systems for preparing compositeprints comprising superposed negative and positive silver images as wellas in additive color processes which may employ this concept and whereinthe film unit is exposed through an optical screen, e.g., a trichromaticadditive color screen of the conventional type to form a developableimage and is then developed with an aqueous alkaline processing fluidincluding a silver halide solvent to form a negative silver image and asilver transfer image of greater density or covering power than thenegative image in a superposed stratum. The resulting composite printmay then be viewed as a color image by light transmitted through theoptical screen. Additive color reproduction systems employing silverdiffusion transfer techniques are per se known and are described, forexample, in U. S. Pat. Nos. 2,726,154 and 2,944,894,

both issued to Edwin H. Land.

By way of illustration a film unit including a transparent supportcarrying an additive color screen, a silver receptive stratum of knowndescription having description including an acid-neutralizing layer.Fol-- lowing development, if the spreader sheet is transparent, it maybe left intact and the resulting structure may then be viewed bytransmitted light as a color transparency. Film units of the foregoingdescription comprising a permanently fixed laminate including a supportcarrying on one surface thereof an additive color screen, photosensitivesilver halide and silver precipitating nuclei are described with greaterparticularity, for example, in U. S. Pat. No. 3,536,488 issued to EdwinH. Land on Oct. 27, 1970; copending applications Ser. No. 889,656, nowUS. Pat. No. 3,615,427 and Ser. No. 889,636, now US. Pat. No. 3,615,426both in the name of Frank E. Debruyn, Jr.; and copending applicationsSer. No. 889,657, now US. Pat. No. 3,615,428 and, Ser. No. 889,660, nowUS. Pat. No. 3615,429 both in the name of Lucretia J. Weed, all filedDec. 31, 1969.

By way of further illustration such a film unit may comprise atransparent polyester support carrying on one side thereof, in order, atrichromatic additive color screen of a conventional type having about500 lines to the inch, a silver receptive stratum comprising copperdeacetylated chitan and 0.25 mgs./ft. coppersulfide,

and a gelatino silver iodochlorobromide emulsion. In accordance withthis invention the film unit may beex posed through the screen toprovide a developable image and then developed by applying a processingfluid of known description including an alkaline material such as sodiumor potassium hydroxide, a silver halide developing agent such as theknown hydroquinones, p-aminophenols, etc., and a silver halide solventsuch as sodium or potassium thiosulfate, sodium thiocyanate, ammoniumthiocyanate, etc., between the thus exposed film unit and the coatedsurface of a spreader sheet comprising a polyester base having coatedthereon a neutralizing layer comprising a 7:3 mixture ofpolyethylene/maleic anhydridecopolymer and polyvinyl alcohol at acoverage of about 1,000 mgs./ft. and a spacer layer comprising a 1:9mixture of styrene/maleic anhydride copolymer and vinyl acetate at acoverage of about 1,000 mgs./ft. Following development the transparentspreader sheet may be retained with the film unit and a resultingsandwich may be employed in known manner by light transmitted throughthe screen to provide a positive color reproduction of the originalsubject matter.

While the preferred photographic systems contemplated by this inventionemploy a transparent sheet, as was mentioned previously it is alsocontemplated that one may in certain systems employ an opaque spreadersheet. It will be appreciated, however, that where transparencies arecontemplated, the opaque spreader sheet must be separated followingimage formation for viewing. lnsystems providing reflection prints, theopaque spreader sheet must also be separated where the print is to beviewed by reflected light from the surface of the film unit insuperposition with the spreader sheet. Where the print is to be viewedby reflected light through a transparent support for the film unit,however, the opaque spreader sheet may be retained. An opaque spreadersheet contemplated by this invention may be prepared by coating on anopaque cellulose Since certain changes may-be made in the above productand process without departing from'the scope of the invention hereininvolved, it is intended that all matter contained in the abovedescription shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:

1. In a photographic process for preparing visible images wherein anexposed photosensitive element ineluding a silver halide layercontaining a developable image is developed by applying an aqueousalkaline processing composition between the thus exposed element and asuperposed spreader sheet employed to facilitate application of saidprocessing composition and to form a visible image only in saidphotosensitive element, the improvement which includes employing as saidspreader sheet a sheet material containing a reagent for substantiallylowering the pH of said processing composition following substantialimage formation, said spreader sheet being retained in superpositionfollowing formation of said image.

2. A process as defined in claim 1 wherein said spreader sheet istransparent.

3. A process as defined in claim 1 wherein said sheet includes apolymeric layer comprising acid capacity effective to lower the pH ofsaid composition upon contact therebetween from a first pH to a secondpH at which said visible image exhibits increased stability.

4. A process as defined in claim 3 wherein said spreader sheet furthercontains a spacer layer to time control the availability of said acidcapacity to contact and thereby lower the pH of said processingcomposition, said polymeric layer being disposed between said sheetmaterial and said spacer layer. I

5. A process as defined in claim 1 wherein said image is in silver.

6. A process for preparing a negative image comprising the steps ofexposing a light-sensitive silver halide layer to form a developableimage; applying an aqueous alkaline processing composition between saidlayer and a superposed transparent element to develop and fix saidimage; and thereafter reducing the pH of said image and said compositionto a lower pH level substantially precluding image instability in theform of tiny transparencies in silver areas of said image whileretaining said transparent element in superposition with said layer.

7.-ln a process for preparing a negative image comprising the steps ofexposing a light-sensitive silver halide layer to form a developableimage and developing said image by contacting said layer with an aqueousalkaline processing composition to form a developed and fixed negativeimage in said layer; the improvement which comprises applying saidprocessing composition in a substantially uniform layer between saidexposed silver halide layer and the coated side of a transparent sheetmaterial bearing a layer of a reagent for reducing after said imageformation the pH of said image and said composition to a lower pH levelsubstantially precluding image instability in the form of tinytransparencies in silver areas of said image.

8. A process as defined in claim 7 wherein said processing compositionincludes a silver halide solvent system comprising a mixture of cysteineand a nitrogenous base.

9. A process as defined in claim 7 wherein said processing compositionincludes a silver halide developing system comprising a high-energy anda lowenergy silver halide developing agent, said low-energy developingagent being present in substantially greater concentration than saidhigh-energy developing agent, the amount of each of said developingagents alone being insufficient to develop appreciable negative density,but said respective amounts together are capable of developing exposedsilver halide to a desired usable density.

10. A process as defined in claim 7 wherein said reagent in said layeron said transparent sheet material comprises a polymeric acid.

11. In a process wherein an exposed silver halide layer containing adevelopable image is developed to form a fixed negative image bycontacting said exposed dipropylamine,

layer with a viscous aqueous alkaline processing composition including asilver halide solvent system comprising the mixture of cysteine and anitrogenous base and a silver halide developing system comprising ahigh-energy aminophenol silver halide developing agent and a low-energysilver halide developing agent selected from the group consisting ofascorbic acids and hydroxylamines, the low-energy developer beingpresent in substantially greater concentration than the high-energydeveloping agent, the amount of each of said low-energy and high-energydeveloping agents alone being insufficient to develop appreciablenegative density, but said respective amounts together are capable ofdeveloping exposed silver halide to a desired usable density;

the improvement which comprises developing said exposed silver halidelayer by spreading said viscous processing composition in asubstantially uniform layer between said silver halide layer and thecoated side of a transparent sheet material having thereon a layer of apolymeric acid reactable with alkaline ions in said processingcomposition to reduce the pH in the environment of said negative image.

12. A process as defined in claim 11 wherein said nitrogenous base is acompound selected from the group consisting of ammonia, sec. amylamine,ethylamine, n-butylamine, allylamine, diethylamine, trimethylamine,triethanol amine, diethylene triamine, triethylene tetramine,N-hydroxyethyl propylene diamine, trimethylene diamine, ethylenediamine, aminoethyl ethanol amine, hydroxyethyl'diethylene triamine,tetraethylene pentamine, guanidine hydrochloride, piperidine,pyrrolidine,,2,5 dimethyl piperazine, polyethylene, imine, symmetricaldimethyl hydrazine and unsymmetrical dimethyl hydrazine; and saidaminophenol contains in a position ortho to the phenolic hydroxyl groupat least one substituent selected from the group consisting of amino,lower alkyl and lower alkoxy groups.

13. A process as defined in claim 11 wherein an inert alkalineion-permeable polymeric layer is disposed over the outer surface of saidpolymeric acid layer.

14. A process as defined in claim 13 wherein said polymeric layercomprises a polyvinyl amide graft silver halide layer; a spreader sheetadapted to be placed in superposition with the side of said film unitcontaining said layer and which is employed to facilitate application ofan aqueous alkaline processing composition between said film unit andsaid spreader sheet subsequent to exposure of said film unit in order todevelop said film unit to form a visible image in said film unit; and aquantity of an aqueous alkaline processing composition adapted forspreading between said spreader sheet and said film unit;

the improvement wherein said spreader sheet contains, on the side ofsaid sheet adapted for superposition with said film unit, a layer of areagent for substantially lowering after substantial image formation thepH of said processing composition applied between said sheet and saidfilm unit to develop said film unit and to form a visible image.

17. A product as defined in claim 16 wherein said support member istransparent.

18. A product as defined in claim 16 wherein said spreader sheet istransparent.

19. A product as defined in claim 16 wherein said spreader sheet furthercontains a spacer layer to time control the availability of saidpolymeric acid to contact and thereby lower the pH of said processingcomposition, said polymeric acid layer being disposed between said sheetmaterial and said spacer layer.

20. A photographic product comprising, in combination, a photosensitiveelement comprising a light-sensitive silver halide layer contained on atransparent support member; a transparent element adapted for placementin superposition with said photosensitive element,

said transparent element comprising a transparent base member carrying alayer of a polymeric acid; and a quantity of a viscous processingreagent adapted for spreading in a substantially uniform layer betweensaid respective elements when in superposition, said processing reagentcomprising a viscous aqueous alkaline solution of a silver halidesolvent system comprising the mixture of cysteine and a nitrogenous baseand a silver halide developing system comprising a high-energyaminophenol silver halide developing agent and a low-energy silverhalide developing agent selected from the group consisting of ascorbicacids and hydroxylamines, the low-energy developer being present insubstantially greater concentration that the high-energy developingagent, the amount of each of said low-energy and high-energy developingagents along being insufficient to develop appreciable negative density,but said respective amounts together are capable of developing exposedsilver halide to a desired usable density.

21. A product as defined in claim 20 wherein said nitrogenous base is acompound selected from the group consisting of ammonia, sec. amylamme,

ethylamine, n-butylamine, allylamine, diethylamine, dipropylamine,trimethylamide, triethanol amine, diethylene triamine, triethylenetetramine, N-hydroxyethyl propylene diamine, trimethylene diamine,ethylene diamine, aminoethyl ethanol amine, hydroxyethyl diethylenetriamine, tetraethylene pentamine, guanidine hydrochloride, piperidine,pyrrolidine, 2,5- dimethyl piperazine, polyethylene imine, symmetricaldimethyl hydrazine and unsymmetrical dimethyl hydrazine.

22. A product as defined in claim 21 wherein said processing compositionis confined in a frangible container.

2. A process as defined in claim 1 wherein said spreader sheet istransparent.
 3. A process as defined in claim 1 wherein said sheetincludes a polymeric layer comprising acid capacity effective to lowerthe pH of said composition upon contact therebetween from a first pH toa second pH at which said visible image exhibits increased stability. 4.A process as defined in claim 3 wherein said spreader sheet furthercontains a spacer layer to time control the availability of said acidcapacity to contact and thereby lower the pH of said processingcomposition, said polymeric layer being disposed between said sheetmaterial and said spacer layer.
 5. A process as defined in claim 1wherein said image is in silver.
 6. A process for preparing a negativeimage comprising the steps of exposing a light-sensitive silver halidelayer to form a developable image; applying an aqueous alkalineprocessing composition between said layer and a superposed transparentelement to develop and fix said image; and thereafter reducing the pH ofsaid image and said composition to a lower pH level substantIallyprecluding image instability in the form of tiny transparencies insilver areas of said image while retaining said transparent element insuperposition with said layer.
 7. In a process for preparing a negativeimage comprising the steps of exposing a light-sensitive silver halidelayer to form a developable image and developing said image bycontacting said layer with an aqueous alkaline processing composition toform a developed and fixed negative image in said layer; the improvementwhich comprises applying said processing composition in a substantiallyuniform layer between said exposed silver halide layer and the coatedside of a transparent sheet material bearing a layer of a reagent forreducing after said image formation the pH of said image and saidcomposition to a lower pH level substantially precluding imageinstability in the form of tiny transparencies in silver areas of saidimage.
 8. A process as defined in claim 7 wherein said processingcomposition includes a silver halide solvent system comprising a mixtureof cysteine and a nitrogenous base.
 9. A process as defined in claim 7wherein said processing composition includes a silver halide developingsystem comprising a high-energy and a low-energy silver halidedeveloping agent, said low-energy developing agent being present insubstantially greater concentration than said high-energy developingagent, the amount of each of said developing agents alone beinginsufficient to develop appreciable negative density, but saidrespective amounts together are capable of developing exposed silverhalide to a desired usable density.
 10. A process as defined in claim 7wherein said reagent in said layer on said transparent sheet materialcomprises a polymeric acid.
 11. In a process wherein an exposed silverhalide layer containing a developable image is developed to form a fixednegative image by contacting said exposed layer with a viscous aqueousalkaline processing composition including a silver halide solvent systemcomprising the mixture of cysteine and a nitrogenous base and a silverhalide developing system comprising a high-energy aminophenol silverhalide developing agent and a low-energy silver halide developing agentselected from the group consisting of ascorbic acids and hydroxylamines,the low-energy developer being present in substantially greaterconcentration than the high-energy developing agent, the amount of eachof said low-energy and high-energy developing agents alone beinginsufficient to develop appreciable negative density, but saidrespective amounts together are capable of developing exposed silverhalide to a desired usable density; the improvement which comprisesdeveloping said exposed silver halide layer by spreading said viscousprocessing composition in a substantially uniform layer between saidsilver halide layer and the coated side of a transparent sheet materialhaving thereon a layer of a polymeric acid reactable with alkaline ionsin said processing composition to reduce the pH in the environment ofsaid negative image.
 12. A process as defined in claim 11 wherein saidnitrogenous base is a compound selected from the group consisting ofammonia, sec. amylamine, ethylamine, n-butylamine, allylamine,diethylamine, dipropylamine, trimethylamine, triethanol amine,diethylene triamine, triethylene tetramine, N-hydroxyethyl propylenediamine, trimethylene diamine, ethylene diamine, aminoethyl ethanolamine, hydroxyethyl diethylene triamine, tetraethylene pentamine,guanidine hydrochloride, piperidine, pyrrolidine, 2,5-dimethylpiperazine, polyethylene, imine, symmetrical dimethyl hydrazine andunsymmetrical dimethyl hydrazine; and said aminophenol contains in aposition ortho to the phenolic hydroxyl group at least one substituentselected from the group consisting of amino, lower alkyl and loweralkoxy groups.
 13. A process as defined in claim 11 wherein an inertalkaline ion-permeable polymeric layer is disposed over the outersurface of sAid polymeric acid layer.
 14. A process as defined in claim13 wherein said polymeric layer comprises a polyvinyl amide graftcopolymer.
 15. A process as defined in claim 11 wherein said polymericacid is present in an amount sufficient to lower the pH in theenvironment of said negative image to below pH
 8. 16. In a photographicproduct comprising a film unit including a support member carrying alight-sensitive silver halide layer; a spreader sheet adapted to beplaced in superposition with the side of said film unit containing saidlayer and which is employed to facilitate application of an aqueousalkaline processing composition between said film unit and said spreadersheet subsequent to exposure of said film unit in order to develop saidfilm unit to form a visible image in said film unit; and a quantity ofan aqueous alkaline processing composition adapted for spreading betweensaid spreader sheet and said film unit; the improvement wherein saidspreader sheet contains, on the side of said sheet adapted forsuperposition with said film unit, a layer of a reagent forsubstantially lowering after substantial image formation the pH of saidprocessing composition applied between said sheet and said film unit todevelop said film unit and to form a visible image.
 17. A product asdefined in claim 16 wherein said support member is transparent.
 18. Aproduct as defined in claim 16 wherein said spreader sheet istransparent.
 19. A product as defined in claim 16 wherein said spreadersheet further contains a spacer layer to time control the availabilityof said polymeric acid to contact and thereby lower the pH of saidprocessing composition, said polymeric acid layer being disposed betweensaid sheet material and said spacer layer.
 20. A photographic productcomprising, in combination, a photosensitive element comprising alight-sensitive silver halide layer contained on a transparent supportmember; a transparent element adapted for placement in superpositionwith said photosensitive element, said transparent element comprising atransparent base member carrying a layer of a polymeric acid; and aquantity of a viscous processing reagent adapted for spreading in asubstantially uniform layer between said respective elements when insuperposition, said processing reagent comprising a viscous aqueousalkaline solution of a silver halide solvent system comprising themixture of cysteine and a nitrogenous base and a silver halidedeveloping system comprising a high-energy aminophenol silver halidedeveloping agent and a low-energy silver halide developing agentselected from the group consisting of ascorbic acids and hydroxylamines,the low-energy developer being present in substantially greaterconcentration that the high-energy developing agent, the amount of eachof said low-energy and high-energy developing agents along beinginsufficient to develop appreciable negative density, but saidrespective amounts together are capable of developing exposed silverhalide to a desired usable density.
 21. A product as defined in claim 20wherein said nitrogenous base is a compound selected from the groupconsisting of ammonia, sec. amylamine, ethylamine, n-butylamine,allylamine, diethylamine, dipropylamine, trimethylamide, triethanolamine, diethylene triamine, triethylene tetramine, N-hydroxyethylpropylene diamine, trimethylene diamine, ethylene diamine, aminoethylethanol amine, hydroxyethyl diethylene triamine, tetraethylenepentamine, guanidine hydrochloride, piperidine, pyrrolidine,2,5-dimethyl piperazine, polyethylene imine, symmetrical dimethylhydrazine and unsymmetrical dimethyl hydrazine.
 22. A product as definedin claim 21 wherein said processing composition is confined in afrangible container.